The methods and systems of the present invention are directed to the modification and improvement of transmissions for automotive vehicles of the type installed by the original equipment manufacturers. The invention is particularly directed to the improvement and modification of the automotive transmissions commonly known as the xe2x80x9c4L80Exe2x80x9d or the xe2x80x9cHydramatic 4L80Exe2x80x9d which are xe2x80x9cfactory installedxe2x80x9d in automotive vehicles manufactured by General Motors Corporation.
The present inventor owns U.S. Pat. No. 5,253,549, issued Oct. 19, 1993 and entitled xe2x80x9cMethods And Systems For Improving The Operation Of Automatic Transmissions For Vehiclesxe2x80x9d; U.S. Pat. No. 4,790,938, issued on Dec. 13, 1988 and entitled xe2x80x9cFilter For Removing Particulate Matter From Fluid Within A Movable Bodyxe2x80x9d; U.S. Pat. No. 4,711,140, issued Dec. 8, 1987 and entitled xe2x80x9cThrottle Valve System For Automatic Transmissionxe2x80x9d; U.S. Pat. No. 4,449,426, issued on May 22, 1984 and entitled xe2x80x9cLaminated Separator Plate Means For Recalibrating Automatic Transmissionxe2x80x9d; U.S. patent application Ser. No. 08/333,552, filed Nov. 2, 1994 and entitled xe2x80x9cMethods And Systems For Improving The Operation Of Transmissions For Motor Vehiclesxe2x80x9d (now U.S. Pat. No. 5,540,628, issued Jul. 30, 1996); U.S. patent application Ser. No. 08/494,844, filed Jun. 26, 1995 and entitled xe2x80x9cMethods And Systems For Improving The Operation Of Transmissions For Motor Vehiclesxe2x80x9d (now U.S. Pat. No. 5,624,342, issued Apr. 29, 1997); U.S. patent application Ser. No. 08/515,098, filed Aug. 14, 1995(now U.S. Pat. No. 5,730,685, issued Mar. 24, 1998) and entitled xe2x80x9cMethods And Systems For Improving The Operation Of Transmissions For Motor Vehicles; U.S. patent application Ser. No. 08/595,810, filed Feb. 2, 1996 (now U.S. Pat. No. 5,743,823, issued Apr. 28, 1998) entitled xe2x80x9cMethods And Systems For Improving The Operation Of Transmissions For Motor Vehiclesxe2x80x9d; U.S. patent application Ser. No. 08/697,625, filed Aug. 28, 1996 (now U.S. Pat. No. 5,768,953, issued Jun. 23, 1998) and entitled xe2x80x9cMethods And Systems For Improving The Operation of Transmissions For Motor Vehiclesxe2x80x9d; and U.S. patent application Ser. No. 08/816,715, filed Mar. 13, 1997 (now U.S. Pat. No. 5,820,507, issued Oct. 13, 1998) and entitled xe2x80x9cMethods And Systems For Improving The Operation Of Transmission For Motor Vehiclesxe2x80x9d. The basic operation of transmissions for automotive vehicles is discussed in the aforementioned patents and patent applications, and these patents and patent applications are expressly incorporated by reference into the disclosure of the present patent application.
The basic principles of operation of the factory installed General Motors 4L80E transmission for automotive vehicles, including the specific modes of operation thereof and the hydraulic circuits and interrelationship of hydraulic circuits, are well known to those skilled in the automotive transmission art. Attention is respectfully invited to the operations manual and text entitled HYDRA-MATIC 4L80-E TECHNICIAN""S GUIDE (1990), published by General Motors Corporation, said publication describing in detail the operation of the xe2x80x9cfactory installedxe2x80x9d 4L80E General Motors transmission, including a discussion of the structure, the hydraulic circuits, and the interrelationship between the structure and the hydraulic circuitry and fluid flow during normal operation of the transmissions in automotive vehicles. The disclosure of the aforementioned publication in its entirety is expressly incorporated by reference into the disclosure of the present patent application as disclosing and illustrating background material known to those of ordinary skill in the automotive transmission art.
In the original design of the 4L80E xe2x80x9cfactory installedxe2x80x9d transmission, the first gear ratio cannot be obtained above a vehicle speed of approximately 35 miles per hour. (See the aforementioned General Motors Corporation publication). A primary object of the present invention is to enable the driver of a vehicle having a 4L80E General Motors transmission to select first gear at any time, thereby enabling the driver to obtain a xe2x80x9cfirstxe2x80x9d gear ratio whenever the gear selector lever is placed in the xe2x80x9c1xe2x80x9d position without regard to the actual vehicle speed and engine rotational speed. This objective is accomplished by modification of the structure and operation of the existing hydraulic circuits of the original transmission and the addition of a new hydraulic circuits to the original transmission.
It is also desirable to modify the xe2x80x9cfactory installedxe2x80x9d automotive transmission to result in quick application during upshifts and quick release forces during downshifts with minimum ratio sharing (overlap) during gear changes, for improved performance particularly when the vehicle is operated at high performance conditions such as racing applications. This object is obtained by varying the structure and operation of the hydraulic circuits of the original transmission to enlarge or reduce existing orifices to control the apply and release fluid flow through the hydraulic circuits, in conjunction with the modification of different spring and pressure values of the pre-existing hydraulic circuits of the factory installed transmission.
Other objects, improvements and advantages of the present invention will become apparent to those skilled in the art from the following description in conjunction with the drawings.
Methods, apparatus and systems are provided for modifying the structure, operation, and functional relationship of structure in xe2x80x9cfactory installedxe2x80x9d transmissions for automotive vehicles. In accordance with the present invention, the transmission identified as 4L80E installed in General Motors Corporation vehicles are modified to enable the driver to obtain a first ratio whenever the gear selector is placed in the first position without regard to actual vehicle speed or engine rotational speed. In the original xe2x80x9cfactory installedxe2x80x9d transmission, the first ratio cannot be obtained for vehicle speeds exceeding approximately 35 miles per hour. The original transmission is modified to achieve this result by providing a fluid flow passageway between the manual valve and a xe2x80x9c1-2xe2x80x9d shift valve to apply sufficient fluid pressure to one end of the shift valve to maintain it in a downshifted (first gear) position whenever a gear selector operatively associated with the manual valve is moved into the first gear selection position. Means are provided to prevent exhaust of fluid through the added passageway when the manual valve (and the gear selector lever) is not in the first gear selection position.
The present invention also modifies the aforementioned xe2x80x9cfactory installedxe2x80x9d automotive transmission by producing quick xe2x80x9cappliesxe2x80x9d and xe2x80x9creleasesxe2x80x9d with minimum ratio sharing (overlap), which is advantageous in improving performance when the vehicle is used for high performance operations such as racing. These further modifications to the operation of the original transmissions are achieved by enlarging or reducing (or plugging) orifices in the original hydraulic circuitry to modify fluid flow therethrough for controlling the apply and release fluid flow. Additionally, adjustments are made to spring and pressure values of the original transmission hydraulic circuitry.
Accordingly, the object of the present invention is to modify the operation of existing xe2x80x9cfactory installedxe2x80x9d automotive transmissions, and in particular the General Motors Corporation 4L80E transmission, to result in changes to the hydraulic circuitry and fluid flow therethrough to enable the driver of the vehicle to select first gear ratio without regard to actual vehicle speed or engine rotational speed, and to produce quick applies and releases which are particularly advantageous for high performance applications. Other advantages and improvements of the methods, systems and apparatus of the present invention will become apparent to those skilled in the automotive transmission art from the following discussion in conjunction with the enclosed drawings.